Network device and auto detecting method for direct link thereof

1. An auto detecting method for direct link, comprising:

sending, by a first network device, a first signal having a specific pattern which comprises a switching sequence of a plurality of transmission speeds of a physical layer to a second network port of a second network device, wherein a first network port of the first network device is connected to the second network port of the second network device in a cable manner;

determining, by the first network device, whether the first network port receives a second signal having the specific pattern from the second network device;

determining, by the first network device, that the first network device directly links to the second network device when the first network device receives the second signal having the specific pattern from the second network device;

determining, by the first network device, that the first network device does not directly links to the second network device when the first network device does not receive the second signal having the specific pattern from the second network device; and

setting a time length of a detecting period by the first network device according to a random number algorithm, so as to detect the second signal having the specific pattern sent by the second network device during the detecting period.

2. The auto detecting method for direct link as claimed in claim 1 , wherein the specific pattern is a combination of signals of a physical layer.

3. The auto detecting method for direct link as claimed in claim 1 , wherein the specific pattern comprises a switching sequence of connection states of a physical layer.

4. The auto detecting method for direct link as claimed in claim 1 , further comprising:

sending the first signal having the specific pattern to the second network port of the second network device by the first network device through the first network port when the detecting period is ended.

5. The auto detecting method for direct link as claimed in claim 1 , further comprising:

executing the step of determining whether the first network port receives the second signal having the specific pattern from the second network device during a first detecting period;

determining whether an accumulated detection times is smaller than a threshold when the first detecting period is ended and the first network port of the first network device does not receive the second signal having the specific pattern sent by the second network port of the second network device; and

accumulating the accumulated detection times by the first network device, and re-executing the step of determining whether the first network port receives the second signal having the specific pattern sent by the second network port of the second network device during a second detecting period when the accumulated detection times is smaller than the threshold.

6. The auto detecting method for direct link as claimed in claim 1 , wherein the first network port or the second network port comprises a physical data port such as an Ethernet port or a fiber-optic network port.

7. A first network device, comprising:

a first network port; and

a network interface circuit, coupled to the first network port, and configured to send a first signal having a specific pattern which comprises a switching sequence of a plurality of transmission speeds of a physical layer to the first network port, wherein the first network device sends out the first signal having the specific pattern from the first network port of the first network device to a second network port of a second network device through a cable network, the first network device determines whether the first network port receives a second signal having the specific pattern from the second network port of the second network device, when the first network device receives the second signal having the specific pattern from the second network device, the first network device determines that the first network port directly links to the second network device, when the first network device does not receive the second signal having the specific pattern from the second network device, the first network device determines that the first network device does not directly links to the second network device, and the first network device sets a time length of a detecting period according to a random number algorithm, so as to detect the second signal having the specific pattern sent by the second network device during the detecting period.

8. The first network device as claimed in claim 7 , wherein the specific pattern is a combination of signals of a physical layer.

9. The first network device as claimed in claim 7 , wherein the specific pattern comprises a switching sequence of a plurality of transmission speeds of a physical layer.

10. The first network device as claimed in claim 7 , wherein when the detecting period is ended, the first network port of the first network device sends the first signal having the specific pattern to the second network port of the second network device.

11. The first network device as claimed in claim 7 , wherein the first network device determines whether the first network port receives the second signal having the specific pattern from the second network port of the second network device during a first detecting period; when the first detecting period is ended and the first network device does not receive the second signal having the specific pattern from the second network device, the first network device determines whether an accumulated detection times is smaller than a threshold; and when the accumulated detection times is smaller than the threshold, the first network device accumulates the accumulated detection times, and re-determines whether the first network port receives the second signal having the specific pattern sent by the second network port of the second network device.

12. The first network device as claimed in claim 7 , wherein the first network port comprises a physical data port such as an Ethernet port or a fiber-optic network port.